The known type of catalysts for dehydrogenating ethylbenzene to styrene are based on iron oxide (Fe.sub.2 O.sub.3) and comprise, as promoters and stabilizers, oxides of alkaline and alkaline-earth metals, oxides of elements of the lanthanide series, and oxides of metals of the sixth group of the periodic table.
The composition of the catalysts, expressed as a percentage of oxides by weight, comprises 50-92% iron oxide, 5-20% alkaline metal oxide, 0.5-14% alkaline-earth metal oxide, 2-10% oxide of elements of the lanthanide series and 0.5-6% oxide of metals of the sixth group.
Preferred compositions, expressed as oxides, comprise iron oxide, potassium oxide, calcium and/or magnesium oxides, cerium oxide and molybdenum and/or tungsten oxides.
In the catalysts, the iron oxide is partly present in the form of potassium ferrate.
Potassium ferrate is considered to be the active catalytic component.